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Introduction to Web Services

Introduction to Web Services. Presented by Sarath Chandra Dorbala. Outline. Definitions Basic Standards SOAP WSDL UDDI. Definitions.

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Introduction to Web Services

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  1. Introduction to Web Services Presented by Sarath Chandra Dorbala

  2. Outline • Definitions • Basic Standards • SOAP • WSDL • UDDI

  3. Definitions • A Web Service is a software component that is described via WSDL and is capable of being accessed via standard network protocols such as but not limited to SOAP over HTTP.www.oasis-open.org/committees/wsia/glossary/wsia-draft-glossary-03.htm • The W3C defines a Web service as a software system designed to support interoperable Machine to Machine interaction over a network. http://en.wikipedia.org/wiki/Web_service • An Internet hosted application controlled through SOAP requests which returns results as SOAP responses. http://www.gateway2sms.com/glossary.asp

  4. Basic Standards • XML • All web service documents are written in XML • XML Schemas are used to define elements used in Web Service communication • SOAP • Communication is done over SOAP (typically) • Request and responses messages are encoded in SOAP • The body of the message is contained with in SOAP envelope • Binds the client to the web service

  5. WSDL • Describes the web service and defines functions that are exposed in the web service • Defines SOAP message format • UDDI • UDDI is used to register and look up services with a central registry • Service Providers can publish information about their business and the services that they offer • Service consumers can look up services that are available by • Business • Service category • Specific service

  6. SOAP • Stands for Simple Object Access Protocol • It is a platform independent, XML bases communication protocol for message exchanging between applications

  7. Elements of SOAP message • SOAP is a XML document with the following elements • Envelope • Used to identify the SOAP message • Header (Optional) • This element contains header. For this course this part is important for incorporating security into web services • Body • This element contains call and response information • Fault (Optional) • This element contains details about processing errors

  8. Skeleton SOAP Message <?xml version="1.0"?> <soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope" soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"> <soap:Header> ... ... </soap:Header> <soap:Body> ... ... <soap:Fault> ... ... </soap:Fault> </soap:Body> </soap:Envelope>

  9. Sample SOAP Message SOAP Request POST /InStock HTTP/1.1 Host: www.example.org Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope" soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"> <soap:Body xmlns:m="http://www.example.org/stock"> <m:GetStockPrice> <m:StockName>IBM</m:StockName> </m:GetStockPrice> </soap:Body> </soap:Envelope>

  10. SOAP Response HTTP/1.1 200 OK Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version="1.0"?> <soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope" soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"> <soap:Body xmlns:m="http://www.example.org/stock"> <m:GetStockPriceResponse> <m:Price>34.5</m:Price> </m:GetStockPriceResponse> </soap:Body> </soap:Envelope>

  11. WSDL • WSDL stands for Web Service Description Language • It is an XML Document that describes a web service • It specifies the location of the service and operations it exposes

  12. Elements of WSDL • <portType> • It describes a web service, the operations that can be performed, and the messages that are involved. • <message> • Defines the data elements of an operation. Eg, Parameters to the function call parameters • <types> • Defines the data types used by the web service • <binding> • Defines the message format and protocol bindings for each port

  13. Skeleton WSDL Document <definitions> <types> definition of types........ </types> <message> definition of a message.... </message> <portType> definition of a port....... </portType> <binding> definition of a binding.... </binding> </definitions>

  14. WSDL Binding to SOAP

  15. UDDI • UDDI stands for Universal Description, Discovery and Integration • UDDI is a platform-independent framework for describing services, discovering businesses, and integrating business services by using the Internet.

  16. Advantages of UDDI • Finding the right business from millions • Defines how to enable e-commerce once business is found • Describing services and business processes programmatically in a single, open and secure environment.

  17. Basic Mechanism

  18. Conclusions • We have seen the essential components of a Web Service. • We have seen the brief overview of these components that form the building blocks of a web service

  19. Recommendations • Examine the real WSDL documents and realize its components • Here is a sample WSDL http://cs.odu.edu/~sdorbala/wsdl/joft.wsdl • Tutorials for creating web services both in .NET and in Java are available http://cs.odu.edu/~sdorbala/ws/JavawebInstr.pdf http://cs.odu.edu/~sdorbala/ws/instructions_net2003.pdf

  20. References • http://wikipedia.org/wiki/Web_service • http://w3schools.com

  21. Questions

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